NAME Frosty Wooldridge

AGE 61

KNOWN FOR His e-mails, blogs, letters and books about overpopulation, and by extension, immigration.

HE SAYS "You can ignore reality, but at some point reality will not ignore you. In the U.S., we're now on track to add 100 million people in the next 30 years. We can bring about population stabilization graciously and gracefully, or nature will do it brutally."

TRAINING Graduated from Michigan State University with a teaching degree, served in the Army Medical Service Corps as a second lieutenant in Georgia and Texas

From his rants decrying overpopulation as "the human Katrina," one might expect Frosty Wooldridge to be a wild-eyed curmudgeon living in a shack at the end of a dirt road, typing on an ancient computer powered by a bicycle contraption. But the 61-year-old man who answers the door of the McMansion in a Denver suburb is sober and clean-cut, with a brownish-gray comb-over and a friendly expression.

No doubt about it, though, Wooldridge is a man on a mission. He compares himself to his heroes: Susan B. Anthony, Martin Luther King Jr., Eleanor Roosevelt, Mohandas Gandhi, Mikhail Gorbachev, Edward Abbey, John Muir and Nelson Mandela. "I'm in front of a wave," he says. "Anyone who steps up is in front of a wave. Anthony for suffragettes, King to bring equality to all people. What I want to do is to create a sustainable and functioning planet, not just 10 years from now, but 100 years from now."

To that end, he devotes every day to spreading the word about overpopulation. He presents free programs to colleges, rotary meetings, Mensa clubs, retired Rocky Mountain News employees - in fact, pretty much anyone who asks. He writes books (seven of them so far, including, most recently, Immigration's Unarmed Invasion). He blogs. He sends material to more than 100 radio hosts, and to the big TV names: Larry King, Ellen DeGeneres, Charlie Rose.

In his personal life, Wooldridge is equally driven. In college, he made a list of goals, and he's been working through it for the past 40 years, checking off items as he goes.

One of his goals was to bicycle across seven continents. He's crossed that off his list. "Traveling awakens your mind, your awareness - especially when you're on a bicycle going 12 miles an hour over a 16,000-foot pass on a gravel road in a snowstorm," he says. "I've been literally every place on the planet on my bike. When you travel through Mexico, through Bangladesh and India, you see the consequences of human growth - unsustainable, unviable human growth - and you see populations living in misery. Most cultures are a product of their religions and their traditions. They don't change, and they suffer the consequences." Wooldridge notes that the United States population would be balanced with a 2.03 fertility rate (children born per woman) - except for immigration. (The nation's current fertility rate is 2.1, the highest since 1971, with Hispanic birthrates in the U.S. at 3.0.) "Unfortunately, in 1965 we started taking on an extra million, then an extra 2 million. One million legal, 2 million illegal, minimum 3 million per year. We're now on track to add 100 million people in the next 30 years."

Wooldridge acknowledges that the immigration issue elicits strong emotional responses. He's been called a xenophobe, but says he's a humanist out to help humanity. He's been tagged as a racist, but he believes that he's a practical thinker.

He points out that Mexico's population grew from 50 million to more than 100 million people in the last century, and will double again in this century. Wooldridge's solution to the porous border is to secure it "like the DMZ in Korea, with 37,000 troops."

He has his critics. The statistics and the assertions that pour from him in a stream are disputed by other experts, including folks at the Pew Hispanic Center and the IRS. "The idea that you can control overpopulation through border control is absurd," says Robin Baker of The Bell Policy Center in Denver. "It's like trying to shut out the real world by living in a gated community." She says gender inequality, poverty and the lack of effective reproductive education are the key factors in overpopulation.

But Wooldridge says he'll continue to spread his version of the word. Last year, he rode his motorcycle 20,000 miles across 48 states on what he dubbed the "Paul Revere Ride," alerting the country to the population crisis. He gave 96 television interviews, appeared in 90 papers and on 60 radio shows. "I don't care if I get called names," he says. "I understand the emotions. I was given the American dream, to enjoy a great experience throughout my life, and I'd like to pass it on to others."

The author is HCN's online editor.